1. Field of the Invention
The present invention relates to an image display apparatus, which is provided with a plurality of display units disposed in tandem on a line of sight of an observer and controls images displayed on the respective display units so as to provide the observer with a three-dimensional image, as well as an image displaying method.
2. Description of the Related Art
As conventional apparatuses capable of displaying images three-dimensionally, various types of such apparatuses are proposed or commercialized. For example, as an electrically rewritable apparatus capable of displaying images three-dimensionally, a liquid crystal shutter-glasses system, etc., is well known. This liquid crystal shutter-glasses system takes pictures of a three-dimensional object using a camera from different directions, combines image data including parallax information obtained into one image signal, inputs the signal into a two-dimensional display apparatus and displays it. An observer wears liquid crystal shutter-glasses, which, for example, allow light to pass through the right eye-liquid crystal shutter and cause the left eye-liquid crystal shutter to shield light for odd fields. On the other hand, the liquid crystal shutter-glasses allow light to pass through the left eye-liquid crystal shutter and cause the right eye-liquid crystal shutter to shield light for even fields. At this time, an image for the right eye is displayed in odd fields in synchronization with an image for the left eye in even fields so that the observer watches the images including parallax between the right eye and left eye through the respective eyes, and thereby obtains a three-dimensional image.
Furthermore, there is a display apparatus, which includes a plurality of two-dimensional display apparatuses that are disposed in tandem in a direction of the line of sight of the observer, allows the observer to watch those images displayed overlapped and thereby recognize the overlapped image as a three-dimensional image though those images are discrete images in the depth direction. On the other hand, there is a display apparatus, which provides variations for brightness of images displayed on two-dimensional display apparatuses to eliminate the situation of those discrete images so that the observer feels as if the object exists at a midpoint of discrete positions and has more naturally a feeling in three dimensions. For example, there is a proposal of a brightness modulation type three-dimensional display system which displays images of an object from a plurality of display apparatuses overlapped with one another using a plurality of half-mirrors and allows a semi-transparent object to be displayed or allows an object behind to be seen through, as described for example in Japanese Laid-Open Patent Application No. 2000-115812.
Such a display apparatus, which is provided with the plurality of display units disposed in tandem on a line of sight of an observer, has a predetermined viewing position at which the observer is provided visually with the three-dimensional image. The above-mentioned viewing position is specific to the display apparatus. No presence of observer in the predetermined viewing position makes it difficult or impossible to provide visually the observer with a three-dimensional image, thus involving technical problems.
In addition, even when an observer views images displayed on the display units in the predetermined viewing position, the observer's visual function, which differs on an individual basis, may make it difficult or impossible to provide visually the observer with a three-dimensional image, thus involving technical problems.